Radio reception and direction finding system



L. A. TAYLOR 2,08,522

RADIO RECEPTION AND DIRECTION FINDING SYSTEM- July 16, 1935,

Filed June 12, 1931 Figl.

H is Attorney- .20 factorilyffor directive purposes' RADIO RECEPTION AND DIRECTION Y V FINDING srs TE w j 1.

LaurensIA..Taylor,'Schenectady, N.Y., assignor to General Electric ,Company, a corporation of;

New Yorlg Application tune 12,- 193i;,seria1-no; 543,907 I m I My inventionrelates to radio reception 1 and direction. finding systems, more particularly for use on aircraft; and it has for one of its objects to provide .a simple, economical and practical 5 means whereby afcommon radio receiving apparatus employed on an aircraft for non-directive re ception; as for receipt of messages, .iweather re'-- ports, etc., may also be employed for determining the dir'ection fromwhichthe received signals are transmitted.

- "A further object of myi nve ntion is to provide a novel coupling means whereby a;1oop maybe.

connected to the signal translating apparatus for either directive, or non-directive reception; 1

of the craft and at the sametimeioperate satis l'he novel-features which I believe to be char.-

acteristic. of my inven'tion' are set forth with particularity in the appended claims. inven-' tion-itself, however, both 'as to its" organization and method of operation; together i with further objects" and advantages thereof, may bestbe understood by referenceto the following descrip tion' taken in {connection with the accompanying ment of my'invention; and'Figs. 'ZxandBrep-resent methods of mountingthe.lodpJantenna; employed in the arrangement; shown Fig. l upon' aircraft.

'Referring to Fig. 1 8a thedrawing I hav shown therein at l aradio "receiver which maybe one of any of the usual constructions employed oni'air craft for the reception of messages, weather-ire nected to ground. A pair of headephon'es .S'is arranged to be connected to the. output circuit of the receiver through a double throw switch I. As

- non-directive radiofrecept'ion, thereceived os'cil lation'sbeing impressed upon the antenna 2 and supplied through the-blocking condenser 5.110 the input of the receiver wheretheyare amplified and detected and the audioicurrients,lreproduced in Still afurtherobject of my invention is'to provide means whereby the loop employed for direc tive reception may be mounted directlyupo'n and in close proximity to the inetallicwing structure;

7 drawing in which Fig. '1 represents an 'embodi of,"the' outer ends of'the conductors on'the two 9' thus arranged the receiver. isladapted forordinary I ifs as (of 5041 if the output circuit thereof s upplied to the head-.-

To providen'ieans whe'reby the "radio-receiver I, may also be employed for determining the direc? tionof the source of the received signals a loop. '5. antenna li is' also "arranged upon the craft, means being provided wherebyethe loop antenna may be 'coupl'e'd to theiinput'of' the radio receiver either for directive or non-directive reception.

j The=a'ntenna 8 may be arranged in any suitable way upon the shaft,'but preferably it is arranged upon the wings, shown in Figs. 2 and 3. Thus, for example","if the craftis oneof the monoplane type the loop may comprisea conductor extending from end to end of the wing thereof, as in-- dicated by the dotted line 9 iii Fig.2. The outer ends of this conductor, at' points' remote from the fuselage, nay then be' connectedby addi-' tional c'onductors Iii and l 'l to a point lowon the" fuselage of'the aircraft and thence carried into 20' thecockpitand'connected to the receiving equipment. P As thus arranged the conductors 9, H] and ll comprise'the'loopwhieh is employedin accordance with my invention. -It'will of course be understood that this loop "may comprise a single turn or a plurality of turns as desired. Y

. In :Fig; 3, I haveshowna similar arrangement for use upon a craft of the biplane type, the loop comprising 'one or, more, conductors 9 arranged upon the wingsand extending lengthwise therewings abeing connected together by additional conductors [2, which may be'carried along one of the lwingstr'uts, or supports, these conductors allbeing' indicatedby dottedrlines in Fig. 3. p p

The loop 8 is arrangedzto be connected to the receiver I either for' "directive; or non-directive reception byl. meansot switches r l 3 and A and a coupling device. indicated as a transformer? l5. When theswit'ch I3 is. in either its right-hand position or T' its-Sleft-hand position, :the' loop is con nejcted through tuning; or loading; inductances M to' theiprimary, winding of" a transformerl5, thev secondary'lwindingof whichis connected across the input of the radio receiver. through the switch 4 in its lower position; .The amount of inductance H! which is connected in circuit with the loop, andlikewise, thenumbe'r of turnsl upon the winding of the transformer l5 which are employed, may be right-hand position. A condenser I6 is connected across the primary winding of the transformer l5 thereby to tune the circuit of the loop to the frequency which it is desired to receive.

To cause the loop to'operatewith the desired de- .i

'gree of directivity, the transformer l5 has an electrostatic shield l6 between it's primary and secondary windings, which shield is connected to ground. The purpose of this shield is to prevent electrostatic effects between the primary winding and the secondary winding and to permit arrangement of the primary windingin such a way that opposite sides of the central point thereof are equally balanced capacitively with respect to ground. I

While I have particularly mentioned'the use of a transformer as the coupling device I5, it will be understood that other forms of coupling means may be employed, it being necessary only. that the input terminals thereof be balanced with respect to ground.

prises the condenser It, the two tuning, or loading,

coils M and the loop structure, all .connected'in. series, the coupling device being connected directly across the condenser. The two coils I4 are connected in opposite sides of the circuit and are so arranged as to maintain the capacitive balance of the loop withrespectto ground. The condenser i6 is also of such construction thatthe capacitive balance. of the loop circuit is maln tained. The loop 8is connected between the two inductances." In this way the voltage across the loop, or the voltage between any portion ofthe loop conductor and ground isv very smalhthe principal voltage-,offthe loopcircuit beingset up across the condenser I6'and therinput tothe coupling device. This is very important to the use of a wing'loop of the type which I have described since it permits mounting of the loop di-.

be had notwithstanding the 'factithat the loop' is mounted directly upon 'the metallicvmembers of the framework of the craft. Thisfurtherperrnits 'theloop' to be stream lin'ed into the structureof the craft, if desired, so as to offer practically no wind resistance and to be unnoticeable upon thecraft.

' The'transformerilB.is then one having high mutual inductance thereby effectively to transfer the loop circuit directly between the gridan cathode of the input discharge device. f To produce. non-directive reception from th loop, a number of different expedients may be employed; It has been found satisfactoryf-for this purpose, to destroy the balanceof the loop by grounding one sidefthereof and to connect the oppositeside" to the 'ung'rounded' input terminal of the receiver. This is done'by operating the switch is" to the middleposition and the switch t to'theupper' position; q 1

Whenjthe switch i3 is in its middlepositi'on, one side of the loopfis connected 'through'the lefthand blade" of the switch to ground; i. e.;to the in its upper position, tothe input grid'terminal 2,oos,522

substantially V r us suppose thatthe antenna 2 is reeled in and of the radio receiver. As thus connected the loop has very little or nodirective effect andmay be employed, for example, for the reception of weather reports and the like.

The receiver I may be .of any suitable construction such as is commonly employed upon aircraft'for the reception of messages such as weather reports. Where thereceiverl is of the simple tuned radio frequency and detector type,

the detector preferably should be regenerative stantially greater than currents produced in the 'detector'due to modulation of the carrier wave, as for example, the frequencies corresponding to the'program or message with whichithe received carrier is modulated. If the receiver be of the superheterodyne type, then the second detector 7 1 is preferably regenerative andisiso'arranged that As thus arranged thecircuit of the loop comithe desired, beat note is produced between the;- oscillations generated in the detector and the intermediatefrequency supplied'thereto. If the re-" ceiver be one in which the detector is not regenerative, then a separate source of oscillations, as indicated at Il, may be employed, this source of oscillations being ofvariable frequency and arranged to'be connected to the input of the de- 7 tector of the receiver, by means of a switch I8 whereby the desiredgaudio beat notes ,are' produced.- .In'a'ny case the intensity of beat note soproduced varies with the intensity ofthe carrier wave supplied to the inputtof the receiver which ,in turn, with the switch is in either its right or left hand position, varies as the craft changes direction'with respect to the direction of propagation of the received waves.

It is preferable that the indication of direction should be produced by visual means and to this,

end a visual indicating device I9 is providedthis indicating device beingconnected between the midpoint or the secondary winding of a trans-- former 20 and both of "the. opposite terminals thereof through unilateral'conducting devices2 I. These devices may be of the copper oxide rectifier type, such as shown in United States Patent No. 1,640,335 to Lars O. Grondahl, issued August 23; 1927. The primary winding of the transformer 26 is arranged'to be connected'to, the output fcircuit'of the receiver through the switch l when in its lower position. Thus by means of theswitch 'L'either the headphones tor the meter!!! may be connected to the output circuit of thereceiver.

To explain the operation of my invention, let

that the operator desires toascertain his direction with reference to'a broadcasting stationthereby to determine'a'routetofollow, or with reference'to two or'more stations'thereby to determine his present location; as by triangulation. j I-Iefirst throws the switch 4 to its upper position and'the switch 3 to its central position thereby to employ the'antenna 8 as a' nondi-' rective antenna. He then tunes the radio receiver I to the'fiequency of the station in the direction of which he wishes to guide the craft- This station may be, for example, a broadcasting station in the vicinityof his destination. Having ascer tained' that the station isitransmitting a signal which is being picked up by the loop, he adjusts the receiver l to produce the above-mentioned beat note in the output circuit thereof. He then throws switch 4 to the lower position and switch l3 either to the left-hand positionjor to the right- V 2,003,522 hand position dependent upon the frequency of the received .carrier wave, and adjusts the con.- denser I 6 to producemaximum response from the meter l9. If itso happens that his plane is directly upon the course leading tothe broadcasting station, the direction of which he desires to determine, littleor no response will be produced by the meter, but as the planeturns either" tion of messages, reports etc may be had with switch l3 in its middle position, switch 4 in its upper position and antenna 2 reeled'in, somewhat better reception may be had with the antenna 2 reeled out. The signal currents produced in the output of the receiver l with the antenna out may be of such intensity that if the meter I9 be connected thereto it is likely to be injured or destroyed. This is also likely to occur with" the antenna in when the craft is in close proximity to broadcasting stations. Toavoid this difficulty a suitable interlock is provided between switches 4 and 1, which is conventionally indicated in the Y drawingas a pair of rods 22 having mutually.

engaging feet thereon and so arranged that when the switch 4 is in its upper position the switch 1 is also looked in its-upper position thereby permitting reception only with the head phones. When the switch 4 is in'its lower position the switch 1 may be ineither position thereby permitting reception either by use of the head-' phones or the meter. a

It will thus be seen that in accordance with my invention, means are provided whereby the receiver which is ordinarily employed upon aircraft may be employed for' direction finding purstations.

the easy reach of the operator.

through actual flights with equipment of the type poses with the addition of a very small amount of auxiliaryequipment. This additional equipment may conveniently be mounted. in a small box upon the side of the cockpit of the aircraft within I have found described that very satisfactory determinations of .direction can bemade from the non-directive signals transmitted from ordinary broadcasting While I have shown a -particular embodiment of my invention,- it will of course be understood that Idonot wish to belimited thereto, since many modifications, both in circuit arrangement, and in the instruments employed, maybe made without departing fr-om thespirit and scope of my invention, as set forth in the appended claims.

What I claim as" new and desire to secure b Letters Patent of theUnit'ed States, is,--

1. A loop circuit for aircraft, comprising a con- .denser, a loop, and a pair of loading coils all connectedin series and tunable to'the frequency to be received, saidloop being mounted in proximity to the metallic portions of the wing structure of the craft, and. said loading coils being connected between each side of the loop and said,

afiected by the metallic portions of the craft, receiving equipment including a transformer having input {terminals capacitivelybalanced with respect to groundfsaid input terminals being connected across said condenser, and said'condenser and loading coils being so arranged that 2. In a direction finding and signal receiving system, a loop antenna, a signal translating device, signal indicating means connected to said signal translating device, means for connecting said loop antenna between the terminals of said signal translating device to produce substantially non-directive reception, a coupling device having its input capacitively. balanced with respect to ground and its output connected to said signal translating device, andmeans for. connecting said loop antenna terminals to the input terminals of said coupling device and to disconnect said terminals from said signal translating devicethereby to produce directive reception.

3. In combination, aloop, a signal translating device comprising an input electron discharge device having a cathode connected to ground and agrid, means to connect said loop between said grid andground thereby to produce non-directive 1 opposite sides of said loop circuit are maintained capacitively balanced with respect to ground.

reception, a transformer having primary and v secondary windings, said connecting means being arranged to disconnect said loop'from said grid and ground and to connect it across said primary winding and to connect said secondary winding between said grid and ground thereby to produce directive reception. 7

4. A loop antenna, signal translating apparatus, means to connect said loop antenna to said signal translating apparatus in such a way as; alternately to produce directive and non-directive response, visual indicating means, audible indicating means, means alternately to connect said visual and audible indicating means to said transmounted upon a mobile craft, a signal translating device having input and output circuits, means alternately to connect said loop to said input circuit in such'a way as to produce relativelynonuniform and uniform reception as the craft changes direction with respect to the direction of propagation of received Waves, said translating device including a detector normally arranged to .demodulate the received carrier wave and supply signal currents to said output circuit, means to produce local oscillations and'to cause said detector to produce a beat note between said local oscillations and the carrier received by said translating device having intensity substantially greater than signal currents produced from the carrier.

waveby detection, and indicating means responsive to the output currents of said translating device whereby an indication may be produced dependent upon the modulation of the said received carrier; when said connecting means is operated for uniform reception and dependent upon the intensity of said received carrier when said connecting means is operated for non-uni form; reception. I

LAURENS 1A. TAYLOR. 

